A magnetostatic wave device is used in a voltage controlled oscillator (VCO), etc., mainly in a microwave band and a quasi-microwave band and has a magnetostatic wave element which generates a magnetostatic wave having a specific frequency depending upon a change in a high-frequency magnetic field.
FIG. 12A shows an example of configuration of a magnetostatic resonator, in which a magnetic garnet layer 6 is formed on part of the surface of a substrate 7 composed of a non-magnetic garnet and striplines 11 and 12 are formed on the surface of the magnetic garnet layer 6. Further, electrode pads 13 and 14 and a stripline 15 are formed on the surface of the substrate 7 with the magnetic garnet layer 6 being present between them. The electrode pads 13 and 14 are connected to ends of the striplines 11 and 12, respectively, and the stripline 15 connects the other ends of the striplines 11 and 12. Each stripline is provided for supplying RF signal for exciting a magnetostatic wave. One of the electrode pads, the electrode pad 14 is connected to a ground conductor, and the other electrode pad 13 is connected to an input/output.
As shown in FIG. 12B, the above magnetostatic wave resonator is disposed between a pair of magnetic poles 17a and 17b of a magnetic field generator. One of the magnetic poles, the magnetic pole 17a also works as a ground conductor. The magnetostatic wave resonator is bonded and fixed to a flat magnetic pole surface 18a of the above one magnetic pole 17a with an electrically conductive paste layer 19, and has a constitution in which a magnetic field perpendicular to the surface of the magnetic garnet layer 6 is applied to the magnetic garnet layer 6.
For example, JP-B-60-26284 and JP-B-58-106814 describe methods of patterning the magnetic garnet layer of the magnetostatic wave device. In these methods, a magnetic garnet layer having some pattern is formed by bonding and forming a resist layer which is composed of a material [SiO.sub.2 or polyimide-containing heat-resistant polymer (PIQ: trade name, supplied by Hitachi Kasei), etc.] insoluble in hot phosphoric acid and has a predetermined pattern to/on part of the surface of the magnetic garnet layer, and then immersing the resultant laminate structure in a phosphoric acid solution having a temperature of several 10.degree. C. to 200 and several 10.degree. C. to etch that portion of the magnetic garnet layer on which no resist layer is formed.